Ashton Kutcher could play a crucial role in putting a serial killer behind bars.

Kutcher is on a list of potential witnesses in the trial of Michael Gargiulo, who stands accused of murdering three women and the attempted murder of a fourth, Radar Online reports.

One of Gargiulo’s alleged victims, 22-year-old fashion student Ashley Ellerin, was dating Kutcher when she was brutally murdered in her Hollywood Hills home.

The night she died, Kutcher, who had just become a household name thanks to That ‘70s Show and Dude, Where’s My Car?, went to see Ellerin at her home around 10pm.

In the statement he later gave to police, Kutcher said he found all the lights on and her car in the driveway, but when he knocked on the door there was no answer.

Looking in the window he saw red liquid on the ground, but assumed it was red wine.

The next day he learned Ashley’s body had been laying just out of view, after she had been stabbed to death.

It took seven years, but police eventually charged Gargiulo after DNA evidence collected from an attempted murder case matched the scene of Ashley’s murder.

Gargiulo, dubbed ‘The Chiller Killer’ because he was an air-conditioning repair man who may have used his line of work to gain access to his victims, also stands accused of two other murders: Maria Bruno, a 34-year-old who was murdered less than two weeks after she moved into Gargiulo’s apartment building in 2005, and the 1993 killing of Tricia Pacaaccio, an 18-year-old woman who was Gargiulo’s neighbor in Illinois at the time.

Kutcher, who is now married to Mila Kunis, has never spoken publicly about the tragic case, but that will change if he’s called to the witness stand.

The Michael Gargiulo trial begins May 2 in Los Angeles.